1. Field of the Invention
The present invention relates to compounds whose structures contain the perovskite units (hereinafter referred to as “perovskite related compounds”).
2. Description of Related Art
Perovskite-type complex oxides and perovskite related compounds exhibit various physical properties. Therefore, they have been used and studied in a wide range of fields.
For example, these materials exhibit physical properties such as anion conduction as oxide-ion conduction, cation conduction as lithium-ion conduction, proton conduction, electronic conduction, ferroelectricity, ferromagnetism, and high-temperature superconduction.
In the perovskite related compounds, materials with layered structures are known. Examples of such materials with the layered structures include:
RP (Ruddlesden-Popper) compounds expressed by a general formula “An+1BnX3n+1”,
DJ (Dion-Jacobson) compounds expressed by a general formula “AnBnX3n+1”, and
Au (Aurivillius) compounds expressed by a general formula “An+1BnX3n+3”. Here A and B represent cations at A and B sites respectively and X stands for anions such as oxide ions at X sites, and n is a natural number.
These solid materials can exhibit unique physical properties due to the layered structures.
For example, in the case of the RP compound, the interstitial oxygen atoms in rock-salt units and/or the oxygen vacancies in the perovskite units are considered to increase the oxide-ion conductivity.
The RP compounds with n=1 are the K2NiF4-type compounds.